Method for sealing leaks in vessels

ABSTRACT

THE INVENTION RELATED TO A METHOD OF SEALING LEAKS IN PIPES, CONDUITS, GAS LINES, CLOSED CONTAINERS, TANKS AND THE LIKE. THE INTERIOR OF SUCH EQUIPMENT IS FIRST PURGED WITH A NON-REACTIVE DRY GAS, SUCH AS NITROGEN, TO REMOVE ANY MOISTURE AND/OR OXYGEN WHICH MAY BE PRESENT. THEN THE SEALANT COMPOSITION IS INTRODUCED INTO THE INTERIOR OF THE EQUIPMENT IN A SUITABLE INERT GAS VEHICLE UNDER PRESSURE. THE SEALANT COMPOSITION IN THE GAS VEHICLE WILL ESCAPE FROM ANY LEAKS PRESENT IN THE EQUIPMENT INTO THE ADJACENT EXTERNAL ENVIRONMENT SUCH AS THE OUTER AMBIENT ATMOSPHERE OR ADJACENT SOIL IN THE CASE OF PIPELINES BURIED IN SOIL. THE SEALANT REACTS WITH OXYGEN AND/OR MOISTURE TO FORM AT THE SITUS OF THE LEAK A SOLID REACTION PRODUCT. THE SEALANT COMPOSITIONS COMPRISE PYROPHORIC VOLATILIZABLE ALKYL ALUMINUM ETHERATES. ILLUSTRATIVE EXAMPLES ARE TRIMETHYLALMINUM DIMETHYLETHERATE, TRIMETHYLALUMINUM DIETHYLETHERATE, AND TRIETHYLALUMINUM DIETHYLETHERATE. THESE AND SIMILAR COMPOUNDS MAY BE USED SINGLY OR IN MIXTURES THEREOF. THEY MAY ALSO BE MIXED WITH VOLATILE ORGANO-SILANE COMPOUNDS IN AMOUNTS RANGING FROM ABOUT 1% TO 99% BY VOLUME. SPECIFIC ILLUSTRATIVE ORGANO-SILANE COMPOUNDS ARE TRIMETHYL ETHOXY SILANE, DIMETHYL DIETHOXY SILANE, AND PROPYL TRIMETHOXY SILANE.

United States Patent O US. Cl. 264-36 7 Claims ABSTRACT OF THE DISCLOSURE The invention relates to a method for sealing leaks in pipes, conduits, gas lines, closed containers, tanks and the like. The interior of such equipment is first purged with a non-reactive dry gas, such as nitrogen, to remove any moisture and/or oxygen which may be present. Then the sealant composition is introduced into the interior of the equipment in a suitable inert gas vehicle under pressure. The sealant composition in the gas vehicle will escape from any leaks present in the equipment into the adjacent external environment such as the outer ambient atmosphere or adjacent soil in the case of pipelines buried in soil. The sealant reacts with oxygen and/or moisture to form at the situs of the leak a solid reaction product.

The sealant compositions comprise pyrophoric volatilizable alkyl aluminum etherates. Illustrative examples are trimethylaluminum dimethyletherate, trimethylaluminum diethyletherate, and triethylaluminum diethyletherate. These and similar compounds may be used singly or in mixtures thereof. They may also be mixed with volatile organo-silane compounds in amounts ranging from about 1% to 99% by volume. Specific illustrative organo-silane compounds are trimethyl ethoxy silane, dimethyl diethoxy silane, and propyl trimethoxy silane.

FIELD OF THE INVENTION This invention relates to sealing leaks in pipes, conduits, closed containers, tanks, and closed systems adapted to contain fluids therein, hereinafter referred to generally as vessel. The invention is particularly adapted for sealing leaks in buried underground piping systems used for conveying fuel gas and also for sealing leaks in telephone and electrical conduits containing nitrogen or other inert gas under pressure.

SUMMARY OF THE INVENTION According to this invention the interior of the vessel is first purged with a dry nonreactive gas, such as nitrogen, to remove moisture and/or oxygen present. The sealant composition is then introduced into the interior of the vessel under pressure in gaseous form or in a suitable inert gaseous vehicle. When the sealant composition escapes through any existing leak in the vessel it reacts with oxygen and moisture present at the exterior locus of the vessel where the leak exists and forms a solid product in situ which seals the leak. The sealant compositions consist essentially of pyrophoric volatilizable alkyl aluminum etherates compounds. These sealant compositions are introduced in the vessel in a non-reactive ice vehicle gas, such as hydrogen, helium or nitrogen in amount so that upon escape of the admixed gas from a leak into adjacent external environment containing moisture and oxygen, such as for example the adjacent soil of a buried pipeline, a seal will be produced. These sealant agents are substances which are easily volatilized and which can be admixed with the inert vehicle gas and carried along with the gas in the vessel.

The sealant com-positions comprise pyrophoric volatilizable alkyl aluminum alkyl etherates. Illustrative compounds are:

Trimethylaluminum dimethyletherate,

3 )3 3)2 Trimethylaluminum diethyletherate, (CH Al.O (C H 2 Triethylaluminum diethyletherate, (C H Al.O (C H 2 Tri-n-propylaluminum diethyletherate,

s 7)3 2 5)2 Tri-n-butylaluminum diethyletherate,

These and similar compounds may be used singly or inmixtures thereof. Other known pyrophoric volatilizable alkyl aluminum etherates having 1 to 4 carbon atoms in the alkyl group may be readily selected by a person skilled in the art.

The alkyl aluminum etherate compounds may be mixed if desired with selected volatilizable organo-silane compounds which have the formula: R Si(OR) wherein R and R is a straight or branched chain alkyl having 1 to 4 carbon atoms, all the alkyls being identical or different, and n and n is an integer from 1 to 4. Specific examples are trimethyl ethoxy silane, dimethyl diethoxy silane, propyl trimethoxy silane, isopropyl trimethoxy silane, butyl triethoxy silane, diisopropoxy dimethoxy silane and tetraethoxy silane. These volatile silanes may be admixed singly or in mixtures thereof with the volatile alkyl aluminum etherate compounds previously described.

The proportions of the volatile alkyl aluminum etherate compounds and volatile organo-silanes may be varied over a wide range depending upon the partial vapor pressures of the specific volatilized components. In general, the proportions of the alkyl aluminum etherate compound may range from about 1% to about 99% by volume, the remainder being the organo-silane compound. It is preferred to keep the alkyl aluminum etherate concentration below 30% by volume in the sealant composition, although higher concentrations may be used, keeping in mind that such higher concentrations may result in pyrophoric compositions which are difilcult to handle. Furthermore, inasmuch as the organo-silanes are generally less volatile than the alkyl aluminum etherate compounds, a greater quantity of the organo-silanes will result in a more even distribution in the vessel or pipeline of the components of the sealant composition due to differences in their vapor pressures. The sealant compositions are not simple mixtures of the alkyl aluminum etherate compounds but in many cases may undergo complex interchange reactions. When such products as well as any of the original components escape from a leak they will react with oxygen or moisture present at the situs of the leak to form complex solid reaction products that seal the leak. Also in the case of vessels or pipelines buried in the soil the escaping sealant compositions will react with the oxygen or moisture present in the soil at the external situs of the leak and form a solid seal while at the same time the soil adjacent the solid seal will provide a matrix or reinforcement for the seal.

The concentration of the volatile sealant compositions used and the pressure of the vehicle gas used may be varied over a wide range depending upon the specific components used, the nature and size of the leaks which are to be sealed and the environmental conditions of the particular vessel and the like. The time of flow of the sealant composition can also be greatly varied accordingly in order to seal existing leaks.

These sealant agents may be added to vehicle gases in concentrations ranging from about 0.005 to about by weight in the vehicle gases. They may also be conveniently added in solutions of suitable hydrocarbons, such as butane, hexane, heptane, etc. which will uniformly volatilize or disperse in the vehicle gas. When the admixed gases escape into the atmosphere they produce in situ a solid seal.

If desired, the sealant compositions may be supplied to the user in containers or cylinders mixed in the proportions required for specific sealing operations. The compositions may be introduced into the vessel and the like by suitable means in controlled or metered amounts in the vessel which has been previously flushed and dried with an inert gas. The inert gas and the added sealant composition are maintained at a suitable pressure for a sufiicient period of time to seal any leak present. Also if desired, the user may be supplied with a suitable container having under pressure an inert gas and the selected sealant agents mixed therein in suitable proportions which can be introduced directly into the vessel and the like. Also if desired, the specific components of the sealant composition can be introduced in volatilized condition separately in controlled amounts in the vessel and the like in which the inert gas is present under suitable pressure.

ILLUSTRATIVE EXAMPLES The following are illustrative procedures for producing seals.

Example 1 A steel pipe section (7 feet long, diameter) drilled with an A;" hole to simulate a leak is buried under 30" of clay loam soil of 6% moisture content. One end of the pipe is connected to a valve-controlled feed line connected to a source of dry nitrogen gas for purging the pipe of any moisture or oxygen, and also as an inert gas carrier for the sealant composition. The nitrogen line is also connected to a bubbler vessel containing the liquid sealant composition. Pressure and how indicators and monitors are also connected in the feed line. The other end of the test pipe is connected to a valved outlet line connected to a pressure gage and pressure recorder. The test pipe is first purged with a stream of dry nitrogen gas to remove oxygen and moisture. Liquid trimethylaluminum dimethyletherate is placed in a bubbler and nitrogen gas passed through the liquid, at ambient temperatures at a pressure of l p.s.i.g. The nitrogen gas, carrying the volatilized trimethylaluminum dimethyletherate vapors is passed into the test pipe until a seal is obtained. An eifective seal can be made after a 72-hour period in which the initial flow rate is 50 c.f.h. at 1# p.s.i.g. Pressure is kept constant and flow rate decreased as sealing takes place.

Example 2 A mixture of 20% trimethylaluminum diethyletherate and 80% dimethyl diethoxy silane, by volume, is placed in the apparatus described above in Example 1 and nitrogen gas is passed through the solution for a period of 200 hours. At the end of this period a seal is obtained which shows no leakage at 100 lbs. p.s.i.g. over a 24 hour period as ind cated Via the flow meter.

ADVANTAGES The present invention is particularly suitable for sealing leaks caused by corrosion in pipelines buried in the soil as well as in the joints. In cases where bell and spigot joints for example are packed with caulked jute or other fibrous materials they tend to dry out and cause leaks especially when the pipelines are used to convey natural fuel gas which is extremely dry. Fuel gas lines buried underground in cities are also subjected to earth heaving and vibration caused by vehicles and trucks of the street trafiic which produce leaks at the joints. The repair of such leaks is very costly because sections of the gas main must be exposed by excavating the superposed soil to gain access to the leaking joints for rescaling them. According to the present invention excavations are tntirely eliminated. The section of the pipeline in which a leak exists is first dried internally by passing a stream of dry gas such as nitrogen. The sealant composition is then fed in a uitable gas vehicle through this section of the pipeline for a sufficient time until the leak is sealed, The sealant compositions of the present invention upon escape from leaks in such underground pipelines react with moisture and oxygen present at the situs of the leak to form a solid complex reaction product and at the same time the adjacent soil provides a reinforcing matrix for the seal. Such seals are impervious to fuel gas and are strong enough to withstand high pressures.

Inasmuch as the sealants which are used in the present invention react with oxygen and/or moisture in the air when they initially escape from any existing leaks in a vessel they produce a visible smoke which serves to locate the situs of the leak. After a lapse of time the leak is sealed as previously explained, but if the seal is broken again it will be automatically resealed if the sealant is present in the interior of the vessel. In the case of systems and pipelines which convey a stream of fluid a selected sealant may be supplied to the stream at all times in suitable concentrations so that any leak which may develop will be automatically sealed when the sealant escapes.

I claim:

1. The method of sealing leaks in a vessel and the like adapted for containing a fluid therein which comprises the steps of introducing into the interior of said vessel a sealant composition comprising a volatilizable pyrophoric alkylaluminum alkyletherate wherein the alkyl has 1 to 4 carbon atoms, applying pressure on the interior of said vessel to permit escape of said sealant composition from a leak present in said vessel into the ambient environment and for a period of time sufiicient to form a solid seal at the situs of the leak.

2. The method of sealing leaks in a vessel and the like as defined in claim 1 wherein the pyrophoric alkylaluminum etherate is selected from the group consisting of trimethylaluminum dimethyletherate, trimethylaluminum diethyletherate, triethylaluminum diethyletherate, tripropylaluminum diethyletherate and tributylaluminum diethyletherate.

3. The method of sealing leaks in a vessel and the like as defined in claim 1 wherein the sealant composition contains a volatile organo-silane compound having the formula: R Si(OR) wherein R and R is a straight or branched chain alkyl having 1 to 4 carbon atoms, the alkyls being identical or ditferent, and n and n is an integer of 1 to 4.

4. The method of sealing leaks in a vessel and the like as defined in claim 2 wherein the sealant composition contains a volatile organo-silane compound selected from the group consisting of trimethyl ethoxy silane, dimethyl diethoxy silane, propyl trimethoxy silane, isopropyltrimethoxy silane,, diisopropoxy dimethoxy silane, butyltriethoxy silane and tetraethoxysilane.

5. The method of claim 1 in which said sealant composition is introduced in admixture with a vehicle gas inert thereto.

5 6. The method of claim 1 in which the interior of said 3,198,167 8/1965 Bakish et a1. 117l07.2 vessel is first purged to remove air and moisture therefrom. 3,356,777 12/1967 Barrett 264-36 7. The method of claim 6 in which the purge is per- 3,508,962 4/1970 Manasevit 117227 formed by displacement by an inert gas.

5 ROBERT F. WHITE, Primary Examiner Clied G. AUVILLE, Assistant Examiner UNITED STATES PATENTS 2,990,295 6/1961 Breining et a1. 117106 D CL 3,114,970 12/1963 Whitacre 117-1072 117106A; 26485 

